Near-threshold ${\pi }^{-}$ photoproduction on the deuteron

The first experimental investigation of the near-threshold cross section for incoherent ${\pi }^{-}$ photoproduction on the deuteron $\gamma$ d -> ${\pi }^{-}$ pp is presented. The experimental technique involved detection of the ~131 MeV gamma ray resulting from the radiative capture of photoproduced ${\pi }^{-}$ in the target. The total cross section has been measured using an unpolarized tagged-photon beam, a liquid-deuterium target, and three very large NaI(Tl) spectrometers. The data are compared to theoretical models that give insight into the elementary reaction $\gamma$ n -> ${\pi }^{-}$ p and pion-nucleon and nucleon-nucleon final-state interactions.